## Cryptology ePrint Archive: Report 2009/505

Authenticated Key Exchange Protocols with Enhanced Freshness Properties

Hai Huang, Zhenfu Cao

Abstract: In this paper, we investigate the security model for authenticated key exchange protocols. We observe that there is further room to extend the latest enhanced Canetti-Krawczyk (eCK) model.

We further enhance the freshness definition for the three-pass authenticated key exchange protocols such that our new definition gives the adversary more capabilities. We point out that the three-pass authenticated key exchange protocols generically transformed from the two-pass authenticated key exchange protocols secure in the eCK model can not be secure in our new security definition. We then introduce a new authenticated key exchange protocol SIG-DH$^+$ and prove that it satisfies our new definition.

Category / Keywords: cryptographic protocols /